The present invention relates to a separator for a fuel cell.
Separators for fuel cells typically have passages for fuel gas and oxidation gas. While flowing through the passages, fuel gas and oxidation gas are consumed in power generation, so that the amount of the gases decreases gradually. Such consumption of gases changes the pressure of the gases in the passages. That is, the amounts of diffusion of the fuel gas and the oxidation gas are changed in the power generation electrodes. Thus, the diffusivities of fuel gas and oxidation gas to the power generation electrodes are uneven depending on the position, which lowers power generation performance.
Japanese Laid-Open Patent Publication No. 2000-223137 discloses a separator that includes recesses forming passages for fuel gas and oxidation gas. The passages have a smaller width at the outlet than at the inlet. Thus, the above mentioned document states that the structure improves the gas diffusivity even if the amount of fuel gas and oxidation gas is reduced while flowing.
The separator having the conventional structure disclosed in the above document has protrusions over the entire surface of a center of the separator, and the back of the protrusions are used as passages. However, the width of each passage gradually decreases toward the outlet, and the width of the protrusion is not uniform. This can warp or distort the separator.